[Sbcl-help] threads vs aref/gethash

Which of the following operations are thread-safe, i.e. in which of the
following (if any) a thread can access a global variable without the
need for a locking mechanism?
a) aref
b) aref [1]
c) setf aref
d) setf aref [1]
e) gethash
f) gethash [2]
g) setf gethash
h) setf gethash [2]
[1]: with the added restriction that the subscript is different for each
thread
[2]: with the added restriction that the key is different for each thread
also, svref instead of aref, if that makes any difference.
thanks
giovanni